1. Field of the Invention
The present invention relates to optical communication and data storage equipment and, more specifically, to manufacturing of semiconductor devices, e.g., semiconductor lasers and traveling-wave photodetectors, that have coated facets.
2. Description of the Related Art
Semiconductor lasers are used in a variety of applications, e.g., optical communication systems, optical storage devices, printers, and copiers. In a typical manufacturing process, semiconductor lasers are fabricated using a wafer having an appropriate layered structure for the active (i.e., light-generating) region of the laser. The wafer is cut into bars, each of which is essentially a one-dimensional laser array. The manufacturing process then involves application of thin films of glasslike materials to the terminal sides, called facets, of the laser bar to define laser cavities. These thin films are usually referred to as facet coatings. Due to the nature of the facet coating process, the coating material can overspray and cover unmasked areas of the laser bar in addition to the facets. In particular, overspray coating of the top and bottom surfaces of the laser bar is undesirable because those surfaces have bonding (e.g., gold) pads for mechanical and/or electrical connections.
For certain applications, optical power/wavelength requirements are such that an individual semiconductor laser cannot provide adequate optical power and/or selection of wavelengths. To provide a suitable light source for some of those applications, laser bars are not cleaved into individual lasers, but rather, two or more laser bars are stacked to form a two-dimensional laser array. One example of such an array is disclosed in U.S. Pat. No. 5,835,515, the teachings of which are incorporated herein by reference. A typical prior-art process of stacking the laser bars involves (i) hardware fixtures for aligning the bars and (ii) special gasket inserts for masking off the bonding pads from overspray coating. As provided in U.S. Pat. No. 5,989,637, the teachings of which are incorporated herein by reference, a gasket insert is a relatively sophisticated piece of hardware that can add significantly to the complexity of the manufacturing process. Disadvantageously, aligning the laser bars, manufacturing gasket inserts, placing the inserts between the stacked bars, and then removing the inserts from the slots between the bars to provide access to the bonding pads after the facet coating process is completed can significantly complicate the process of manufacturing two-dimensional laser arrays.